Cardiopulmonary resuscitation (CPR) is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. Artificial respiration, such as mouth-to-mouth breathing or a bag mask apparatus, is used to supply air to the lungs. When a first aid provider performs manual chest compression effectively, blood flow in the body is about 25% to 30% of normal blood flow. However, even experienced paramedics cannot maintain adequate chest compressions for more than a few minutes. Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26 Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successful at sustaining or reviving the patient. Nevertheless, if chest compressions could be adequately maintained, then cardiac arrest victims could be sustained for extended periods of time. Occasional reports of extended CPR efforts (45 to 90 minutes) have been reported, with the victims eventually being saved by coronary bypass surgery. See Tovar, et al., Successful Myocardial Revascularization and Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing CPR. In one variation of such devices, a belt is placed around the patient's chest and the belt is used to effect chest compressions. Our own patents, Mollenauer et al., Resuscitation device having a motor driven belt to constrict/compress the chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000); Sherman, et al., CPR Assist Device with Pressure Bladder Feedback, U.S. Pat. No. 6,616,620 (Sep. 9, 2003); Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,066,106 (May 23, 2000); and Sherman et al., Modular CPR assist device, U.S. Pat. No. 6,398,745 (Jun. 4, 2002), and our application Ser. No. 09/866,377 filed on May 25, 2001, show chest compression devices that compress a patient's chest with a belt. Each of these patents is hereby incorporated by reference in their entirety. Our commercial device, sold under the trademark AUTOPULSE®, is described in some detail in our prior patents, including Jensen, Lightweight Electro-Mechanical Chest Compression Device, U.S. Pat. No. 7,347,832 (Mar. 25, 2008) and Quintana, et al., Methods and Devices for Attaching a Belt Cartridge to a Chest Compression Device, U.S. Pat. No. 7,354,407 (Apr. 8, 2008).
These devices have proven to be valuable alternatives to manual CPR, and evidence is mounting that they provide circulation superior to that provided by manual CPR, and also result in higher survival rates for cardiac arrest victims. The AUTOPULSE® CPR devices are intended for use in the field, to treat victims of cardiac arrest during transport to a hospital, where the victims are expected to be treated by extremely well-trained emergency room physicians. The AutoPulse® CPR device is uniquely configured for this use: The the components are stored in a lightweight backboard, about the size of a boogie board, which is easily carried to a patient and slipped underneath the patients thorax. The important components include a motor, drive shaft and drive spool, computer control system and battery.
In certain in-hospital situations, it is desirable to provide chest compressions with the AutoPulse® CPR device while imaging the patient. For example, doctors may wish to continue CPR compressions, or limit any interruptions in compressions, while the patient is placed within advanced imaging devices such an MRI device, fluoroscope system or CT scanner, X-Ray machine or any such imaging device to image the thorax, heart or coronary arteries of the patient, or the head of the patient. This may be needed to assess trauma, visualize a catheter placement, or diagnose organ function. The current AutoPulse®
CPR device can fit within the imaging device, but the number of metal components which would thus fall within the imaging area of the imaging device would make it difficult to obtain a usable image. The metal components create such large and numerous artifacts that the patient's anatomy is poorly visible in imaging devices. Under fluoroscopy, the anterior/posterior view is the most clinically useful view, but is totally disrupted by artifacts caused by the metal components. Under MRI, no images can be obtained at all, while under CT scanning, some useful images may be obtained but they are typically obscured with significant artifacts. When in use, the AutoPulse motor, drive spool and chassis is disposed beneath the heart of the patient, and this creates significant artifact in any scan of the thorax. When in use, the AutoPulse battery is disposed beneath the head of the patient, and this creates significant artifact in any scan of the head. For other mechanical CPR systems, such as the LUCAS® system, the artifact in thorax images is significantly greater. In addition, chest mounted CPR systems, in which significant large mechanisms are mounted above the chest, do not fit into the gantry of many imaging devices (the gantry is the donut-shaped part of the CT scanner that supports moving components as they pass over the patient project and detect x-rays to create a CT image). This includes the LUCAS® device and the THUMPER® mechanical CPR devices.